Jan. 18 (Bloomberg) -- The form of cancer that Apple Inc.
Chief Executive Officer Steve Jobs announced he had more than
six years ago grows and spreads slowly and, in some patients,
the migrating cells aren’t detected for years, doctors said.

Jobs, who announced yesterday he was taking a leave of
absence, had a liver transplant in 2009. That’s a strategy
sometimes taken to stop neuroendocrine tumors that have spread
to that organ, said John Fung, chairman of the Digestive Disease
Institute at the Cleveland Clinic in Ohio. The disease recurs in
about half of those patients, he said.

“That would be the major concern,” said Fung, who hasn’t
treated Jobs and doesn’t know the details of his case, in a
phone interview yesterday. “It wouldn’t be a total surprise.”

Neuroendocrine cancer, which strikes about 3,000 Americans
a year, produces high levels of hormones that disrupt digestion
and other body functions. Jobs’s medical troubles first became
public after a 2004 statement, when he indicated his tumor was
caught and removed. The Apple chief hasn’t given a reason for
the liver transplant he underwent.

The leave of absence taken by Jobs yesterday was his third
since 2004. He has been unable to keep on weight as he undergoes
treatment for his conditions, according to a person with
knowledge of the situation who requested anonymity because the
matter is private.

Steve Dowling, a spokesman for Cupertino, California-based
Apple, declined to comment beyond a company statement that
didn’t include specifics on Jobs’s health.

Infections, Side Effects

“Whether the weight loss is suggestive of a recurrence of
the cancer, that’s speculation,” Fung said, noting that weight
loss may result from a variety of causes, including viral
infections or drug side effects.

In the e-mail to Apple employees, Jobs said he will remain
CEO while Chief Operating Officer Tim Cook will take over the
company’s day-to-day operations.

Patients who undergo liver transplants can experience
“countless” difficulties for years afterwards as they undergo
drug treatment and face possible organ rejection, said Linda
Sher, a surgeon at the University of Southern California Liver
Transplant Program in Los Angeles, who hasn’t treated Jobs and
doesn’t know the details of his case.

“The number of complications that can occur are from here
to the sky,” Sher said yesterday in a phone interview. “I
could spend all day listing them.”

The Apple chief received the liver transplant at Methodist
University Hospital in Memphis, Tennessee. The surgeon who
performed the procedure, James Eason, is an expert in treating
recurrences of neuroendocrine tumor. He didn’t return a call to
his office yesterday seeking comment.

Bile Duct

Liver surgery usually involves cutting and reconnecting the
bile duct, a tube in the body that transports the digestive
fluid. Blockages in the duct sometimes occur at the site where
it was stitched back together, Sher said.

Other complications can occur long after the original
surgery and can take a number of forms, according to Sher, who
is conducting a study to determine which neuroendocrine tumor
patients are most likely to benefit from getting a new organ.

Transplant patients must also take drugs to prevent the
immune system from attacking and rejecting the new organ, she
said. Because they dampen the body’s disease-fighting systems,
drugs most commonly used, cyclosporine and tacrolimus, are
associated with infections, tumors and kidney damage, Sher said.
Patients sometimes take other drugs, such as steroids, that
raise the risk of diabetes, she said.

While most cases of acute organ rejection occur within the
first six months after surgery, the risk of rejection persists
for years afterwards, Sher said. Patients must see their doctors
frequently to adjust transplant medications, monitor liver
function and diagnose complications, she said.

“There are any number of things that can happen,” she
said. “Both the patient and the doctor have to be attentive and
alert.”